An ultrastructural study of granulocytic development in feline bone marrow

Granulocyte development in the bone marrow of foetal cats was studied using cytological smears and transmission electron microscopy. The three types of granulocytes could be distinguished at the promyelocyte stage on the basis of granule content. Neutrophilic promyelocytes had numerous primary (azurophilic) granules while the eosinophilic and basophilic promyelocytes had specific granules. Specific granules had developed in the neutrophil by the myelocyte stage. The appearance of the specific granules was compared to findings in other reports on cat granulocytes, in other animals and in man.